1. Field of the Invention
The present invention relates to an apparatus and a method for preparing composite particulates by which an adhering material is made to adhere to particulates so as to form composite particulates.
2. Description of the Related Art
As a method for causing an adhering material to adhere to an adhesion substrate (a member to which the adhering material is to adhere), there have been known the PVD (physical vapor deposition) method and the CVD (chemical vapor deposition) method. The CVD method is a method in which an adhering material (depositing material) is made to adhere to the adhesion substrate (deposition substrate) by a chemical reaction in a vapor phase. The PVD method is a method in which an adhering material is caused to adhere to the adhesion substrate by thermal vapor deposition, sputtering, ion plating or the like.
Of the CVD method and the PVD method, an appropriate one is selected and used, depending on the material constituting the adhesion substrate and the adhering material. In the cases where the adhesion substrate is particulates, use is often made of the PVD method which has a comparatively wide range of selection of the adhering material, among others, the sputtering method.
The sputtering method is a method in which an anode and a cathode are arranged in a He or Ar gas atmosphere together with an adhesion substrate and an adhering material (target) which are located between the anode and the cathode, and a voltage is impressed between the electrodes, whereby the adhering material is sputtered from the target and made to adhere to the adhesion substrate.
For the cases where the adhesion substrate is particulates, various forms of sputtering apparatuses have been proposed in order to achieve uniform adhesion of the adhering material to the whole part of the particulates.
Examples of the sputtering apparatuses proposed hitherto include a sputtering apparatus in which two cylindrical electrodes are coaxially arranged on the inner side and the outer side and the outer-side electrode is provided with vanes on the inner side thereof (Japanese Patent Laid-Open No. Sho 56-41375), and a sputtering apparatus which is arranged inside a rotary drum for containing a powder along the axial direction (Japanese Patent Laid-Open No. Hei 5-271921).
In addition to the above, a polygonal barrel sputtering apparatus has been proposed which includes a vacuum vessel polygonal in vertical sectional shape, a rotating mechanism for rotating the vacuum vessel, and a sputtering target disposed inside the vacuum vessel (Japanese Patent Laid-Open No. 2004-250771). In this sputtering apparatus, an adhering material is made to adhere to the surfaces of particulates contained in the vacuum vessel while rotating the vacuum vessel.
Also, there has been proposed a method of preparing a composite powder in which a tubular rotary stage and a source of an adhering material located at such a position as to be surrounded by the rotary stage are provided, and the powder is pressed against the inner surface of the rotary stage by centrifugal forces generated by rotating the rotary stage (Japanese Patent Laid-Open No. 2008-45197).